Method and apparatus for installing and retrieving well tools in well strings



Aug. 23, 1966 w. J. HAYES 3,268,006

METHOD AND APPARATUS FOR INSTALLING AND RETRIEVING WELL TOOLS IN WELL STRINGS Filed Sept. 10, 1962 9 Sheets-Sheet 1 INVENTOR WILLIAM J. HAYES HIS ATTORNEY w. J. HAYES 3,268,006

9 Sheets-Sheet 2 HIS ATTORNEY Aug. 23, 1966 METHOD AND APPARATUS FOR INSTALLING AND RETRIEVING WELL TOOLS IN WELL STRINGS Filed Sept. 10, 1962 g- 1966 w. J. HAYES METHOD AND APPARATUS FOR INSTALLING AND RETRIEVING WELL TOOLS IN WELL STRINGS Filed Sept. 10, 1962 9 Sheets-Shet 5 HAYES INVENTOR:

WILLIAM J. W ywzfw HIS ATTORNF Aug. 23, 1966 w. J. HAYES METHOD AND APPAR ATUS FOR INSTALLING AND RETRIEVING WELL TOOLS IN WELL STRINGS Filed Sept. 10, 1962 9 Sheets-Sheet 4 HIS ATTORNEY INVENTOR WILLIAM J. HAYES Aug. 23, 1966 w. J. HAYES 3,263,006

Ag? APPARATUS FOR INSTALLING AND EV G WELL TOOLS IN WELL STEIN S Flled Sept. 10, 1962 9 Sheets-Sheet 5 a l w m 6 7 J M INVENTOR:

WILLIAM J. HAYES HIS ATTORNEY Aug. 23, 1966 w. J. HAYES 3,268,006 METHOD AND APPARATUS FOR INSTALLING AND RETRIEVING WELL TOOLS IN WELL STRINGS Filed Sept. 10, 1962 9 Sheets-Sheet 6 INVENTOR WILLIAM J. HAYES Bwyzz.

HIS ATTORNEY Aug. 23, 1966 w. J. HAYES METHOD AND APPARATUS FOR INSTALLING AND RETRIEVING WELL T Filed Sept. 10, 1962 OOLS IN WELL STRINGS 9 Sheets-Sheet 7 |NVENTOR2 WILLIAM J. HAYES BY: z

HIS ATTORNEY Aug. 23, 1966 w. J HAYES 3 268 METHOD AND APPARATUS FOR INSTALLING AND I RETRIEVING WELL TOOLS IN WELL STRINGS Flled Sept. 10, 1962 9 Sheets-Sheet 8 FIG. 22

FIG. 20

FIG.

INVENTOR:

WILLIAM J. HAYES I BY: V

HIS ATTORNEY g- 1966 w. J. HAYES 3,268,006

METHOD AND APPARATUS FOR INSTALLING AND RETRIEVING WELL TOOLS IN WELL STRINGS Filed Sept. 10, 1962 9 Sheets-Sheet 9 FIG. 24

INVENTOR:

WILLIAM J. HAYES flwfmzm HIS ATTORNEY United States Patent M 3,268,006 METHOD AND APPARATUS FOR INSTALLING AND RETRIEVING WELL TOGLS IN WELL STRINGS William J. Hayes, West Covina, Califi, assignor to Shell Oil Company, New York, N.Y., a corporation of Delaware Filed Sept. 10, 1962, Ser. No. 222,473 Claims. (Cl. 166154) This invention relates to a method and apparatus for running well tools into and out of well strings. More particularly, the invention is directed to a means for installing and retrieving well tools in well strings disposed in underwater wells. The invention has specific application to the running in and retrieving of well tools from well string mandrels disposed at locations inaccessible to conventional running-in and retrieving apparatuses.

The invention is particularly suited for the insertion of a tool, such as gas lift valve, in a preselected pocket of a series of laterally-disposed pockets extending from the sides of a Well production string at axially-spaced intervals therealong. The invention provides means whereby an insertion or retrieving mechanism may be pumped through a production string to a preselected pocket and there 'be activated to insert a tool into said pocket, or retrieve a tool from said pocket. The insertion or retrieving mechanisms are carried by a carrier of sufficient flexibility to pass through curved flow lines and/or wellhead conduits leading to the production or tubing string.

A recent development in the oil industry is the drilling and completion of wells at offshore locations where wellhead assemblies and production control units are positioned beneath the surface of a body of water and preferably close to the bottom of said body of water. The positioning of the wellhead assemblies and control units at the bottom of the body of water has the advantage that it does not present navigation hazards to boats operating in the vicinity of the offshore wells. In addition, positioning wellhead assemblies and production control units at the bottom of the body of water results in considerable savings, since it is not necessary to erect protective stationary platforms around wellheads in the manner presently employed to protect well casings and wellhead assemblies extending above the surface of the water. It has also been found necessary to position wellhead assemblies on the ocean floor in water depths where it is not feasible to erect a stationary platform around the wellhead assembly.

The placement of wellhead assemblies on the ocean floor raises new problems with regard to carrying out workover, maintenance, or other operations in completed wells. Major workover operations call for the use of an operating station in the form of a barge, platform or vessel positioned on the surface of the water above the well, together with equipment for going down and entering the wellhead assembly and the tubing and/ or casing strings connected thereto, and in some instances may require the entire removal of the wellhead assembly to the surface. In order to carry out some of the more simple workover or maintenance operations, such as the perforation of well casings, the opening of a packer, the removal or insertion of a valve, the cleaning of a paraflin from a tubing string, etc., it has been necessary to develop an entirely new line of well tools which can be pumped through a well string from some remote location, often a mile or more from the well. Upon entering the well with such tools, the tool passing through the well string is positioned therein for carrying out some preselected operation. After completing the operation, the tool in the well string is removed, generally by reverse circulation.

3,268,906 Patented August 23, 1966 While the problem of pumping a tool'to the bottom of a well tubing string in order to carry out certain operations is fairly readily solved, the problem of pumping a certain tool to a preselected position within the well string is far more difiicult. This is especially true where it is necessary to position the tool in one of a series of similar locations within the well string. For example, in inserting or removing a gas-lift valve in a well string provided with a series of valve mandrels at spaced intervals along the length of the string, it is necessary to determine the position of the mandrel desired to be worked upon.

In the past, well tools, such as gas lift valves, have been run into selected positions in well strings through means of wire line devices extending to the top of the well. Such devices were generally lowered into the well string on a wire line and activated by said wire line at a selected depth to force the tool carried by the line into a selected pocket or mandrel. In this case, the length of the wire line run into the well string indicated the depth of the tool within the well string and, forces imported through the wire line at selected depths were utilized to activate a seating mechanism secured to the wire line and operatively engaging a tool carried thereby.

The above-described wire line systems proved effective when used in land based wells having relatively straight strings extending into the earth. In such wells, tools secured to wire lines descend directly down the well string by virtue of their weight and the weight of the wire line secured thereto. The environment surrounding offshore wells is, however, critically different from that of the land 'based wells. In offshore wells having wellhead assemblies disposed on the bottom of a body of water, the line of communication between the well and cooperating surface or underwater operating or workover stations includes lengths of tubing or flow line extending between the stations and the wellhead assembly. Due to the relatively large depths encountered in offshore drilling operations, ranging in hundreds of feet, it is diflicult or impossible to maintain the tubing or flow lines extending between surface stations and the wellhead assemblies in a straight condition. For this reason, these flow lines are flexible to some extent, and generally include curves of varying degrees. Because of these curves, the lowering of tools through the flow line and into the well string through means of land base type wire lines proves difficult, if not impossible. It is believed apparent that the reliance of tool weight to impart movement through a curved flow line will result in hanging up of the tool in the curved and horizontal sections of the flow line and in fouling of the Wire line secured to the tool.

It is noted that curved tubing or flow lines communicating with underwater well strings are not limited to flow lines extending to stations located on the surface of a body of water above the wellhead. For example, it is anticipated that the flow lines may run along the bottom of the body of water to a station disposed on said bottom remote from the wellhead assembly. In the latter case, however, the problems encountered with the use of wire line lowering are still present, since such flow lines are likely to be curved and run along relatively level surfaces on the bottom of the body of water.

From the foregoing discussion, the necessity and advantages of a tool carrier adapted to pass through curved tubing or flow lines extending into underwater well strings is believed apparent. Furthermore, the necessity of selecting mechanisms to be used in combination with such carriers to select preselected pockets or mandrels within the well string is also believed obvious.

It is, therefore, an object of the present invention to provide a method and apparatus to pass well tools through a well string into preselected pockets or mandrels disposed in communication with said well string.

Another object of the invention is to provide an apparatus adapted to be pumped through curved and horizontal sections of flow lines to preselected locations in a well string.

A further object of the invention is to provide an apparatus adapted to pass through a Well string and automatically seat itself in a preselected recess of a plurality of recesses spaced along a well string.

Another object of the invention is to provide a well tool carrier adapted to insert and retrieve well tools in pockets disposed laterally of a well string, said carrier being provided with means to bias a tool carried thereby into or out of a preselected pocket disposed laterally of the Well string.

Yet another object of the invention is to provide a method for installing and removing well tools in pockets disposed laterally of and in communication with a well string located remote from accessible lines of communication therewith.

These and other objects of this invention will become apparent from the following description and accompanying illustrations of the invention.

In its broadest aspect, the present invention provides a method for installing and removing well tools in preselected pockets disposed laterally of and in communication with the interior of a well string. The method comprises securing a well tool to a motor swab and pumping the swab and the tool secured thereto through the well string to a position adjacent the preselected pocket. The tool is then biased into alignment with the pocket and the swab is pumped so as to force the tool secured thereto into engagement with the pocket. The motor swab is then removed from the tool secured thereto and pumped through the well string to an accessible location remote from the preselected pocket. In order to remove a tool from a preselected laterally-disposed pocket of the well string, a tool retrieving mechanism is secured to a motor swab and pumped with said swab through the well string to a location adjacent the preselected pocket. The retrieving mechanism is then biased into alignment with the tool disposed in the preselected pocket and forced into engagement with said tool by pumping of the motor swab. After the retriever has engaged the tool, the motor swab having the retriever and tool connected thereto is pumped in a direction to remove the tool from the pocket. The motor swab, retriever and tool are then pumped, as a unit, through the well string to an accessible location remote from the preselected pocket.

Basically, the well tool installation apparatus of the present invention comprises a carrier adapted to be inserted into a -well string and propelled therethrough by fluid pressure to the approximate location of a preselected tool pocket disposed laterally of and in communication with the interior of the well string. The apparatus further comprises a tool connector carried by the carrier and adapted to release a tool connected thereto upon engagement of said tool in the preselected pocket. Throw-over means are operatively associated with said connector to automatically bias a tool connected thereto into alignment with the preselected tool pocket. In addition to being used as an installation means, the apparatus of the present invent-ion may be used to retrieve tools from pockets disposed in well strings. In the latter application, the carrier member carries a retriever mechanism rather than a tool connector, and the carrier and retriever are adapted .to be inserted into a well string and propelled therethrough into engagement with a tool disposed in a preselected pocket of the well string.

The invention will now be described with reference to the accompanying drawings wherein:

FIGURE 1 is a schematic view illustrating a wellhead assembly positioned on the floor of a body of water;

FIGURES 2 to 6 are diagrammatic sectional views of a well string incorporating an embodiment of the invention being utilized for inserting a gas lift valve into a mandrel disposed in a side pocket of the well string;

FIGURES 7 and 8 are diagrammatic sectional views of a well string corresponding to that shown in FIGURES 2 to 6, illustrating the application of the embodiment of the invention shown therein being utilized in the removal of a gas lift valve from a mandrel disposed in a side pocket of the Well string;

FIGURE 9 is a longitudinal cross-sectional view illustrating the details of the interior structure of an apparatus corresponding to that shown in FIGURE 5;

FIGURES 10 and 1 1 are longitudinal cross-sectional views illustrating the structural details of a gas lift valve securing mechanism adapted to be used with the apparatuses of the present invention and showing insertion and retrieving mechanisms to be used in combination therewith.

FIGURE-S 12 and 113 are longitudinal sectional views illustrating a modified embodiment of a gas lift valve securing mechanism and retrieving mechanism therefor adapted to be used in combination with the method and apparatus of the present invention;

FIGURES 14 to 16 are diagrammatic sectional views of a well string, illustrating the application of another embodiment of the invention being utilized in the insertion of a gas lift valve into a side pocket of the well string;

FIGURES 17 to 20 are diagrammatic sectional views of a well string corresponding to that of FIGURES 14 to 16, illustrating the embodiment of the invention shown therein being utilized in the removal of a gas lift valve from a pocket disposed laterally of the well string;

FIGURE 21 is a longitudinal perspective view illustrating the interior details of the pocket leading to the gas lift valve mandrel illustrated in the embodiment of the invention shown in FIGURES 14 to 20;

FIGURE 22 is a cross-sectional view taken on line 22-22 of FIGURE 21; and

FIGURES 23 and 24 are diagrammatic sectional views of a well string, illustrating the application of an em'bodiment of the invention similar to that of FIGURES 14 through 22, except for the indexing and throw-over appa ratuses used in combination therewith.

Referring now to FIGURE 1, a wellhead assembly is shown as positioned below the surface of a body of water 31 on the floor 32 thereof. The wellhead assembly comprises a platform 33 secured to the top of a conductor pipe or surface casing 34, which in turn extends into the earth below the body of water 31 and is preferably cemented in position. The wellhead assembly 30 is shown as being provided with two or more vertically positioned guide columns 35 and 36 which are fixedly secured at their lower ends to the platform 33. Awell casing head 37 is mounted on the top of the conductor pipe 34 and has a control equipment housing 38 secured thereto. The equipment housing 38 closes the top of the casing head and/ or any casing and tubing suspension equipment employed on the wellhead assembly, as well as various control valves and other control equipment used on the Well.

A pair of flow lines 41 and 42 emerge from the housing 38 in gently sweeping curves from a vertical position. These lines may extend down to a substantially horizontal position and run along the floor 32 to a remote station where fluid from the Well, and normally from other wells, is collected, metered and treated. Alternatively, the lines 41 and 42 may extend upwardly to an operating station located at the surface of the body of water 31 approximately above the wellhead assembly 30. In the case where the lines 41 and 42 extend to collection stations, they may be miles in length, and where the lines extend to surface operating stations they generally measure hundreds of feet in length. In addition to the surface casing 34, the well may be provided with a casing string 43 suspended within the surface casing 34 and. extending downwardly into the formation below the floor 32. In the illustration of FIGURE 1, the flow lines 41 and 42 are in communication with a pair of well or tubing strings 44 and 45 depending within the well. It is to be understood, however, that in installations wherein a single tubing string is utilized, one of the flow lines may be in communication with the annular space between the tubing string and the adjacent well casing. For the purpose of illustrating the present invention, one of the tubing or well strings 44 is shown as being provided with a series of valve housings or side pockets 46 spaced therealong wherein gas lift valves may be positioned.

Referring now to FIGURES 2, 3, and 4, a section of the well string 44 having a side pocket 46 disposed in the wall thereof is shown extending through a portion of the casing string 43. Although the casing string 43 is not illustrated throughout the figures of the drawings, it is to be understood that it would generally assume a position corresponding to that illustrated in FIGURE 2. Furthermore, although the following description is directed to the illustrated section of the string 44 and a side pocket 46 thereof, the description is equally applicable to any section of the string 44 having a side pocket disposed in the wall thereof. The pocket 46 includes a recessed guide section 47 converging towards a gas lift valve mandrel 48 disposed at one end thereof. The mandrel 48 includes a seating shoulder 50 and detent shoulders 51, shown in detail in FIGURES and 11, adapted to position and facilitate locking of a gas lift valve within the mandrel, as will be developed subsequently. The exterior end of the mandrel 48 is provided with openings 52 and 53 extending therethrough to facilitate fiuid fiow through a valve disposed within the mandrel. As clearly shown in FIGURES 3 and 4, the well string 44 is provided with a selector or stop recess 54 disposed beneath the pocket 46 in close proximity thereto. The recess 54 includes a lower shoulder 54a which, together with stop elements secured to a tool carrier, to be described subsequently, functions as indexing means to direct tools to a preselected pocket 46.

In FIGURES 2, 3, and 4, an embodiment of the tool insertion apparatus of the invention is shown in the sequential positions that it assumes during the insertion of a gas lift valve into a valve mandrel disposed in a preselected pocket 46 of the well string 44. The apparatus comprises a carrier member 55 including spaced and connected motor swabs 56 and 57, and a flow valve 58 communicating with said motor swabs. The interior details of the motor swab and flow valve are shown in FIGURE 9. The operation of the flow valve and motor swabs secured thereto is described in copending application Serial No. 45,036, filed July 25, 1960. As described in the copending application, the flow valve and motor swabs used in combination therewith are adapted to be pumped through conduits by fluid pressure exerted on either end of the swab and valve combination. Through utilization of either one or the other of the motor swabs 56 and 57, fluid pressure exerted on the combination forces the carrier member up or down within a conduit, such as the well string 44, wherein the motor swabs are being used. Preferably, the carrier member 55 includes at least two sets of motor swab and valve combinations, as illustrated in FIGURE 2, said sets being connected to each other and spaced apart a distance at least equal to the open length of side pockets 46 of the well string 44. Through such an arrangement, it is assured that at least one set of the motor swabs will be subjected to fluid pressure when the insertion apparatus is passing by a side pocket in the well string.

The carrier member 55 of the embodiment shown in FIGURES 2 to 9 has an indexing or position selector device 59 secured thereto above the upper flow valve 58. The indexing device 59 includes a pair of dogs 61 normally carried in a retracted position and adapted to extend into engagement with the indexing recess 54 in the well string 44. The indexing device 59 is provided with a mechanism to urge the dogs 61 into an extended position upon reaching a desired location in the well string and, thus the dogs 61 engage a preselected recess 54 and prevent continued downward movement of the insertion apparatus. A preferred form of extending mechanism to be used in the indexing device 59 is illustrated in my copending appiication Serial No. 56,855, filed September '19, 1960.

In order to provide for the conveyance of a tool, such as a gas lift valve, the carrier member 55 has secured thereto through the indexing device 59 a throw-over mechanism 62 and a releasable tool connector 63. FIG- URES 2 to 4 illustrate the throw-over mechanism and tool connector in their operative positions, with a gas lift valve 64 secured releasably in the tool connector 63. The throw-over mechanism 62, as illustrated in detail in FIGURE 9, is of relatively conventional construction, including toggle links 65 pivotally secured to a springbiased slidable sleeve 66 and toggle links 67 pivotally secured to the free ends of the links 65 and extending into pivotal engagement with a fixed sleeve member 68. Through this arrangement, the spring-biased sleeve 66 acts continuously to force the pivotally-connected ends of the toggle links into engagement with the walls of a conduit, such as the well string 44, through which the throw-over mechanism is passing and functions to force the throw-over mechanism and any structure secured thereto towards and into recesses encountered in the conduit. Thus, as shown in FIGURE 4, the throw-over mechanism forces the tool connector, gas lift valve, and carrier structure into the pockets 46 as the throw-over mechanism passes these pockets.

The tool connector 63, as illustrated in detail in FIGURE 10, includes alternating guide fingers 70 and collet fingers 71 adapted to operlatively engage -a locking mechanism 72 secured to the valve 64. The locking mechanism 72 is provided to secure the valve 64 within the tool mandrel 48. In the engaged condition shown in FIGURE 10, the fingers 70 and 71 act to hold the locking mechanism 72 and the valve 64 secured thereto in alignment with respect to the connector 63. The collet fingers 71 also act to secure a locking mandrel 73 of the locking mechanism 72 in the unlocked position. The locking mechanism 72 includes pivoted latching dogs 74 resiliently biased through slots 75 in the sides of the mechanism housing by a spring-biased piston 76. The latching dogs 74 are shaped to receive a head secured to the inner end of the locking mandrel 73 and thus be secured in position extending through the slots 75. A spring 77 is positioned to bias the mandrel 73 into locking position against the dogs 74, as illustrated in FIGURE 11.

In operation of the locking mechanism 72, when the valve 64 is inserted into the mandrel 48 as illustrated in FIGURE 10, the latching dogs 74 are forced inward by the walls of the mandrel, thus pressing the piston 76 against its biasing spring. When the valve is fully inserted, a shoulder 78 on the locking mechanism 72 seats against the shoulder 50 of the mandrel 48 and the latching dogs 74 are caused to expand below the detent shoulders 51 by the spring-biased piston 76. At this point, the latching dogs 74 hold the valve in the mandrel 48 with sufficient force to permit the collet fingers 71 of the connector 63 to be pulled out of engagement with the locking mandrel 73. Upon release of the locking mandrel 73 from the collet fingers 71, the head of the mandrel 73 is biased between the latch- 'ing dogs 74 by the spring 77 and, thus the dogs are held in locked engagement with the shoulders 51. The latter condition is illustrated in detail in FIGURE 11.

FIGURES 2 to 4 illustrate the application of the abovedescribed apparatus in inserting a gas lift valve 64 into a selected mandrel 48 by one method. It is noted, that although these figures show only one pocket 46 and mandrel 48 on the tubing string 44, the string actually includes a series of such pockets in spaced longitudinal relationship. The carrier 55, having the indexing device 59, throw-over mechanism 62, connector 63, locking mechanism 72, and valve 64 secured thereto is first pumped down the well string 44 as indicated by the arrows in FIGURE 2. After being pumped down through the well string 44 to a desired location below the selected mandrel 48, the latching dogs 61 of the .indexing device 59 spring into engagement with the shoulder 54a at the bottom of a reces 54, as illustrated in FIGURE 3, and thus prevent further downward movement of the carrier. At this time, as indicated in FIG- URE 4, the flow of fluid in the well string 44 is reversed to an upward direction by pumping fluid down an adjacent tubing string or down the casing-tubing annulus, and the carrier 55 with the respective components secured thereto are moved upwardly. As the carrier member moves upwardly, the upper slanted surfaces on the dogs 61 slide out of the recess 54 and the throw-over mechanism 62 acts to force the tool connector and valve 64 into alignment with the valve mandrel 48. Continued upward movement of the carrier then acts to force the valve 64 into engagement with the mandrel 48, as illustrated in FIGURES 5, 10, and 11. After the valve is seated in the mandrel, flow in the well string 44 is reversed to a downward direction, thus pulling the connector out of engagement with the locking mandrel of the valve and returning the indexing device to the engaged position in the recess 54, as shown in FIGURE 5.

After the valve 64 has been sea-ted in the mandrel 48 and the components of the insertion structure have been returned to the recess 54, as shown in FIGURE 5, the insertion apparatus is in condition to be removed from the well string 44. In order to remove the apparatus from the well string, a carrier member 81 having motor swabs and valve means corresponding to the carrier'member 55 is pumped down the well string towards the insertion apparatus as illustrated in FIGURE 5. The carrier member 81 has secured to the lower end thereof a spear 82 adapted to pass into the connector 63 and engage the collet finger 71 thereof. The spear 82, as illustrated in detail in FIGURE 9, includes a pointed head adapted to pass into and engage the resilient collet fingers 71 of the connector 63.

After the spear has engaged the collet fingers 71, flow in the casing string 44 is reversed, as illustrated in FIG- URE 6, and the carrier members and the entire string of components secured thereto are pumped through the string 44 to an accessible location such as a workover barge, where they may be removed from the line of flow through the well string 44.

The above-discussed carrier member 55, described with reference to its application in the insertion of a gas lift valve, may also be utilized with a retrieving tool to remove such valves from side pocket mandrels into which they have been installed. In order to utilize the carrier 55 for retrieving tools, the connector 63 is removed therefromand a retriever 84 is substituted in its place. The carrier member 55, having the retriever 84 secured thereto, is then pumped through the well string 44 to the recess 54 in a manner corresponding to that described with reference to the use of the carrier in the insertion of a gas lift valve. After the dogs 61 of the indexing device 59 have engaged the recess 54, the flow in the tubing string 44 i reversed and the carrier member and components secured thereto are pumped upwardly, as illustrated in FIGURE 7. As the carrier member is pumped upwardly, the throw-over mechanism 62 biases the retriever into alignment with the valve 64 seated in the mandrel 48. Continued upward movement of the carrier forces the retriever into engagement with the locking mandrel 73, as illustrated in FIGURE 11. Flow in the well string is then again reversed to a downward direction and the carrier is forced downwardly, thus removing the retriever and the valve 64 engaged therein from the mandrel 48 and side pocket 46. During the removal of the valve 46 from the mandrel 48, the head of the locking mandrel 73 is pulled from between the latching dogs 74, and elements of the locking mechanism 72 function in a manner corresponding to their operation during insertion of the valve. After the locking dogs on the indexing device 59 of the carrier are reengaged in the recess 54, the carrier and the components.

secured thereto are in connection to be removed from the well string.

In order to remove the carrier member 55 and the retriever and valve secured thereto from the well string, a carrier member 81, as described previously, having a retriever 84 substituted for the spear 82 is pumped through the well string 44 to the valve 64 as illustrated in FIG- URE 8. Upon reacting the valve 64 the retriever 84 secured to the carrier 81 engages a pointed head on the valve in a manner corresponding to the engagement between the retriever and locking mandrel illustrated in FIGURE 11. After the retriever 84 engages the pointed head of the removed valve, the carriers 55 and 8-1, and the components secured thereto, are pumped upwardly through the Well string 44 to an accessible position where they may be removed from the flow through the well string.

FIGURE 11 illustrates the interior details of the retriever 84 described previously with reference to FIG- URE-S 7 and 8. The retriever 84 includes resilient spaced collet fingers 85 having outwardly extending ends of hooked shaped configuration adapted to grasp the pointed end or fishing head of the locking mandrel 73 or a pointed end on a gas lift valve, as illustrated in FIGURE 8. The retriever further includes a stop member 86 interposed between the fingers 85 and shaped to receive and limit movement of a pointed head member received therein. Through this arrangement, the hooked shaped ends of the fingers 85 are biased apart by a pointed head member entering thereinto and upon complete entrance of the head member the fingers 85 snap into the position illustrated in FIGURE 11, thus locking the head member in the retriever.

FIGURES 12 and 13 illustrate an alternative form of retriever adapted to 'be used in combination with a specific locking mechanism 87. The locking mechanism 87 differs from the aforedescr-ibed mechanism 72 only in that the locking mandrel 88 thereof includes an enlarged shoulder 89 and a guide and detent extension. The retriever 90 to be used in combination with the locking mechanism 87 includes a housing 91 having a pocket 92 formed therein to receive the extension of the mandrel 88. The retriever 90 further includes a flange 93 and stop 94 on the end and intermediate portions, respectively, of the housing 91 and a sleeve 95 slidably received over the flange 93. The sleeve 95 includes necked down portions 96 and 97 disposed on opposite sides of the flange 93 to limit sliding movement of the sleeve relative to the housing 91. In order to facilitate retraction of the sleeve 95, as will be developed subsequently, spring ibiased balls 98 are spaced around the inner periphery of the necked down portion 97 for limited inward extension with respect thereto. A compression coil spring 99 is interposed between the housing 91 and the sleeve 95 to 'bias the sleeve into a normally extended position, as illustrated in FIGURE 13. The retriever 90 is locked to a well too-l inserted therein through means of balls 101 received in tapered openings 10*2 extending through the housing adjacent to flange 96 thereon. The tapered openings 102 are dimensioned to permit the balls 101 to be inserted thereinto from the exterior of the housing 9 1 and are tapered to an extent to permit the balls to extend only partially into the pocket 92. With the sleeve 95 in the extended position, as shown in FIGURE 13, the necked down portion 96 Ibiases the balls 101 into the pocket 92 to the fullest extent. When the sleeve 95 is forced towards the housing 91, as illustrated in FIGURE 12, the balls 101 are permitted to fall into the intermediate section of the sleeve having the enlarged interior diameter.

The operation of the retriever 90 corresponds to that previously described with respect to retriever 84 insofar as its passage through the well string and into engagement with the locking mandrel is concerned. Upon engaging the mandrel 88 of the locking mechanism 87, the balls 98 abut against the shoulder 89 and the sleeve is force to the position shown in FIGURE 12, thus permitting the balls 101 to retract out of the pocket 92. After the sleeve 95 is retracted to the position shown in FIG- URE 12, the necked down portion 96 abu-ts against the stop 94, and the spring biased balls 98 are forced past the shoulder 89, thus permitting the sleeve to extend, through force of the spring 99, to the position shown in FIGU-RE13. As the sleeve extends to the position shown in FIGURE 13, the necked down portion 96 forces the balls 101 into the pocket 92 and into locked engagement with the detent extension of the mandrel 88. At this point, the retriever 90 is secured to the locking mandrel 88 and the valve 64 may :be removed from the valve mandrel 48 in a manner corresponding to that described with reference to the operation of the retriever 84 in FIGURES 7 and 8.

It is noted, that in the embodiment of the apparatus described with reference to FIGURES 1 to 9, the sections of the carrier, the respective components secured thereto, and the valve and locking mechanism therefor are connected to each other through flexible joint means, as by short resilient hose sections -or ball joints 103 and 104. These joints provide for flexibility of the valve, locking mechanism, and the carrier and the components secured thereto, and thus facilitate movement of the apparatus through curved flow lines. The ball joints 103 are of relatively conventional structure, as illustrated in FIGURE 9. The joints 104 between the sections of the carrier member are provided with flow passages to accommodate the use of flow valve 57 as described in copending application Serial No. 45,036, filed July 25, 1960, cited supra. The ball joints 103 between the valve 64 and locking mechanism 72 or 87 and the throw-over mechanism 62 and the connector or retriever secured thereto are surrounded by flexible sleeves 105 fabricated of rubber, neoprene or some other compressible material. The use of the sleeves "105 permits flexing of the ball joints 103 cooperating therewith while the apparatus is passing through curved flow lines and further acts to maintain the valve and connector or retriever cooperating therewith in a normally stiflf position. Maintaining the connector or retriever and a gas lift valve received therein in stiff position with respect to the throw-over mechanism 62 prevents excessive rubbing of a valve carried by the connector or retriever on the walls of a flow line through which the apparatus is passing and also facilitates the guidance of the gas lift valve carried by the apparatus into the side pocket 46 and mandrel 48. It is to be understood that the number of ball connecting joints may be varied, departing upon the degree of flexibility desired, without departing from the invention.

FIGURES 14 and 22 illustrate an alternative apparatus to carry out the tool insertion and retrieving method of the present invention. In these figures, components corresponding to those previously described are designated by the same numerals used heretofore. The apparatus shown in FIGURES 14 to 22 differs from that previously described primarily in the structural details of the carrier member and the indexing evice used in combination therewith. These structural characteristics are, in turn, accompanied by differences in the sequence of operation during the insertion and retrieving of well tools.

FIGURES 14 to 16 illustrate the embodiment of the apparatus shown therein being utilized in the insertion of a gas lift valve 106 into a valve mandrel disposed in the side pocket of a well string. The valve 106 differs from valve 64 only in that it does not include a pointed retrieving head on its leading end. The numeral 107 designates a tubing or Well string through which the apparatus is being pumped. The string includes a series of longitudinally spaced side pockets 108 having mandrels 109 disposed at the lower end thereof. The structural details of the mandrel 109 correspond to those of the aforedescribed mandrel 48. Although only one pocket and mandrel is shown, it is to be understood that a series of similar pockets are located at axially spaced intervals along the string. Each pocket 108 includes a selector channel or groove 111 extending longitudinally therein and terminating at the valve mandrel 109. As clearly illustrated in FIGURES 16 and 21, the groove includes a stepped down or guide section 112 leading into an indexing section 113 of a preselected diameter. To facilitate indexing of a specific valve into a preselected section 113 and the mandrel communicating therewith, each indexing section 113 has a specific interior diameter, and the diameters of the sections in the respective pockets 108 increase from the top to the bottom of the tubing string. The thus dimensioned indexing secions 113 cooperate with specifically dimensioned selector rings 114 carried by the insertion apparatus to perform the indexing function, as will be described in detail below.

In FIGURES l4 and 15, the insertion apparatus is shown being pumped down the tubing string 107 to a preselected side pocket 108. The apparatus includes a carrier 115, preferably including two sets of motor swabs 116 spaced longitudinally from each other by a distance at least equal to the open length of a side pocket 108-. As in the description of the FIGURES 2 to 9 embodiment of the invention, the longitudinal spacing of the motor swabs assures that at least one set of swabs will be subjected to force by fluid pressure at all times fluid is being pumped through the well string 107. The sets of motor swabs 116 have interior details corresponding to those disclosed in copending application Serial No. 807,708, filed April 20, 1959. As described in the copending application, alternative motor swabs in each of the sets 116 provide for a propulsion of the motor swabs in opposite directions, depending on the direction of flow in the well string. The motor swabs 116 differ from the swabs 56 and 57, previously described, in that they do not cooperate with a flow valve, such as the valve 58. Thus, the swabs 116 are not adapted to permit fluid to pass therethrough.

The lower of the motor swabs 116 illustrated in FIG- URE 14 is secured to spacer elements 117. The length and number of spacer elements 117 depends on the flexibility desired and the length of side pocket 108 to be used in combination with the apparatus. The lowermost spacer elements 117 is secured to a throw-over mechanism 62 having a tool connector 63 and valve 106 secured thereto in the manner described with reference to FIGURE 2. In addition, a selector ring 11 of a preselected diameter is secured to the connector 63. It is noted that the pairs of motor swabs 116 and the components secured thereto are connected through means of ball joints 103 corresponding to those previously described with reference to FIGURES 2 to 9, and that the joints between the connector and throw-over mechanism and the valve and locking mechanism and the valve and locking mechanism have flexible sleeves therearound.

In operation, the insertion apparatus is assembled as shown in FIGURE 14- and inserted into a flow line leading to the well string 107 The insertion into the flow line generally takes place at a relatively accessible location, such as an operating station as described with reference to FIGURE 1. As shown in FIGURE 14, the assembled apparatus includes a selector ring 114 adapted to index the tool carried by the apparatus into a preselected side pocket communicating with the side of the well string 107. The selector ring 114 may be either interposed between the throw-over mechanism 62 and connector 63 or secured to the periphery of the connector 63. After the apparatus has been inserted into the flow line, fluid is pumped down the flow line thus subjecting the motor swabs 116 to a differential in pressure and forcing the apparatus down the flow line and into the well string 107. As the insertion apparatus passes through the well string, the throw-over mechanism 62 forces the valve 106 and the components secured thereto into each of the side pockets 108. Upon entering the side pockets, the selector ring 114 carried by the connector 63 slides along the guide section 112 toward the indexing section 113 of the selector groove 111. If the grooves in the guide and .indexing sections of the selector groove are of a diameter smaller than that of the selector ring, the insertion apparatus slides over the edges of the said grooves and back into the well string 107. Since the diameters of the selector grooves increase from the top to the bottom of the well string, the selector ring and the selector grooves act to bypass the insertion apparatus by the side pockets 108 until the desired side pocket is reached. FIGURE 15 shows the insertion apparatus as it is being directed into the well string 107 after by-passing a non-selected pocket.

When the insertion apparatus reaches the first side pocket having an indexing groove of a diameter slightly larger than the selector ring 114, the ring enters the sections 112 and 113, and the valve 106 is directed into the mandrel 109. Thus, the selector grooves and ring cooperate to by-pass the apparatus by pockets having guide and indexing sections of a diameter smaller than the selector ring, and prevent. the apparatus from passing beyond the selected pocket to lower pockets having indexing sections of increasingly large diameter. Upon entering the valve mandrel 109, the valve 106 is locked therein in the manner previously described with reference to the valve 64 in FIGURES 2 to 6. The direction of flow in the well string is then reversed thus pulling the connector 63 out of engagement with the locking mandrel 73 and forcing the insertion apparatus through the well string in an upward direction. The insertion apparatus is then pumped to an accessible location removed from the flow through the well string. The slanted upper faces of the side pockets 108 permit the apparatus to be pumped by the longitudinally spaced side pockets on upward travel of the apparatus.

FIGURES 17 to illustrate the embodiment of the apparatus shown therein in the process of retrieving a valve from a preselected side pocket. In this operation, the apparatus differs from that described with reference to FIGURES 14 to 16 in that a retriever 83, as previously described, is substituted for the connector 63. The retriever 83 has a selector ring 114 secured thereto to index the apparatus in a preselected side pocket. As with the connector 63, the selector ring 114 may be either interposed between the throw-over mechanism 62 and the retriever 83, or secured to the periphery of the retriever 83.

After the apparatus has been assembled as shown in FIGURE 17, it is inserted into the well string 107 and pumped therethrough in a manner corresponding to that described with reference to FIGURE 14. As the retrieving apparatus passes through the well string, the selector ring of the apparatus and the selector grooves of the pockets 108 cooperate to index the apparatus in a preselected pocket in a manner identical to that described with reference to the insertion apparatus of FIGURES l4 and 15. Upon reaching the preselected side pocket, the selector groove 111 guides the selector ring 114 and the retriever 83 secured thereto towards and into engagement with the locking mandrel 73 of the preselected valve 106, as shown in FIGURE 19. FIGURE 18 illustrates the retrieving apparatus by-passing a side pocket having a selector groove with a diameter of less than the selector ring 114.

After the retriever has engaged the locking mandrel 73 of the preselected valve, the flow in the well string 107 is reversed and the apparatus is thus pumped upwardly thereby pulling the valve out of the mandrel 109 in a manner corresponding to that described with reference to FIGURES 7 and 11. The retrieving apparatus and the valve secured thereto are then pumped upwardly through the well string, as shown in FIGURE '20, to an accessible location outside of the flow through the well string. The slanted upper faces of the side pockets 108 facilitate passage of the retrieving apparatus by the side pockets as the apparatus passes upwardly through the well String.

Referring now to FIGURES 23 and 24, therein is illustrated a modified embodiment of the invention adapted to be used with a method similar to that described with reference to FIGURES 14 to 22. In FIGURES 23 and 24, the numeral 120 designates a well or tubing string having longitudinally spaced side pockets 121 and 122 disposed along the length thereof. Although only two side pockets areillustrated, it is to be understood that the well string 120 may include any desired number of such pockets. Each of the side pockets is provided with a gas lift valve mandrel 123 at the lower end thereof corresponding identically with the mandrels 48 and 109 described in detail with respect to the aforedescribed embodiments of the invention. The tubing or well string 120 further includes throw-over springs 124 secured to the inner wall thereof opposite each of the side pockets. The springs 124 are of substantially U-shaped leaf form, as clearly illustrated in FIGURE 24, and have one end 125 fixedly secured to the string 120 as by welding and an opposite end 126 adapted to slidably engage the string 120. Through this arrangement, the springs 124 function to bias elements passing through the string 120 toward the side pockets. The sliding engagement between the end 126 and the string 120 also allows a spring to compress and thus permits elements to pass thereby with very little restriction.

In the insertion apparatus designed to be used with the well string 120 illustrated in FIGURES 23 and 24, the numeral designates a carrier corresponding identically to that described with reference to FIGURES 14 to 22. The insertion and retrieving apparatus of FIG- URES 23 and 24 differs from that of FIGURES 14 to 22 primarily in the details of the indexing apparatus and the aforedescribed throw-out mechanism (i.e. springs 124) used in combination therewith. The indexing apparatus of FIGURES 23 and 24 comprises a spacer element 127 of a preselected specific length adapted to cooperate with specifically dimensioned openings extending between the interior of the well string and the pockets 121 and 122. The spacer element 127 is rigidly secured at its lower end to a connector 63 and is pivotally secured at its upper end to the carrier 115 through a pivot 103. In order to maintain the spacer 127 in axial alignment with the string 120, annular riding members 128 are fixed to the periphery of the spacer element at the upper and-intermediate portions thereof. The annular riding members 128 have a diameter slightly less than that of the tubing string 120 and are fabricated of a material, such as brass, having a low coefiicient of friction.

FIGURES 23- and 24 illustrate the apparatus of the invention shown therein in the process of inserting the gas lift valve 106 into a mandrel 123 communicating with a preselected side pocket 122. To commence this process, the carrier 115, preselected spacer element 127, connector 63, locking mechanism 72 and valve 106 are assembled into the illustrated condition and pumped down the tubing string 120 in a manner corresponding to that described with reference to the application of the invention shown in FIGURES 14 to 16. As the insertion apparatus passes down the well string 120, the spacer element 127 and the valve 106 connected thereto function to by-pass the assembly past unselected pockets, such as the pocket 121 illustrated in FIGURE 23, until the assembly is pumped to the preselected pocket 122. This by-passing or indexing function is accomplished by maintaining the length of the spacer element and the valve 106 secured thereto at a preselected length excessive of that required to permit the assembly to be biased through the openings in the well string 120 communicating with unselected pockets. This operation is believed apparent from FIG- URE 23, wherein the insertion apparatus is shown bypassing a pocket 121 having an opening communicating with the well string of insutlicient length to permit the apparatus to be biased thereinto. From the latter figure, it is also apparent that the riding members 128 function to maintain the assembly in alignment with the well string 120 during the time the assembly is passing unselected pockets. It is noted that the open length of the side pockets increases in descending order along the length of the well string 120 and thus, the assembly will by-pass unselected upper pockets until the first pocket having an opening of sufiicient length to permit the assembly to be biased thereinto is reached. Since the locking mechanism 72, valve 106 and connector 63 are of a fixed length, indexing is controlled by selecting a spacer element 127 of a desired length.

Upon reaching the preselected pocket 122. as illustrated in FIGURE 24, the spring 124 functions to bias the insertion assembly and the valve 106 secured thereto into alignment with the mandrel 123. At this point, continued downward movement of the assembly functions to insert the valve 106 into the mandrel 123 in a manner corresponding to that described with reference to FIGURES 14 to 16. After the valve is inserted in the mandrel, flow in the well string 122 is reversed to an upward direction and the connector 63 is released from the valve-locking mechanism. At this point, the insertion assembly may be removed from the tubing string by pumping the assembly up the well string 122 to an accessible location, such as a workover barge. The inclined upper surfaces of the side pockets, and the inclined lower ends of the springs 124 function to facilitate upward movement of the assembly within the well string 120.

After the insertion assembly has been removed to an accessible location, it may be utilized to remove gas lift valves from preselected side pockets disposed along the length of the well string 120. In order to facilitate this operation, the connector 63 is removed from the assembly and a retriever, such as a retriever 83, is substituted therefor. In order to index the retrieving assembly to a preselected side pocket, a spacer element 127 dimensioned to index in the preselected pocket is incorporated into the assembly. It is noted that a spacer element indexed to a preselected pocket in the retrieving operation must exceed the length of a spacer element indexed to the same pocket for the insertion operation by a length approximately equal to the combined length of the valve 106 and locking mechanism 72, since the latter elements are not secured to the retrieving assembly during the time it is pumped down to the well string 120 to a preselected side pocket. After the retrieving assembly is assembled, it is pumped down the well string 120 and into a preselected pocket in a manner corresponding to that described with reference to the insertion operation. Upon entering the preselected pocket, the retriever 83 secured to the assembly is pumped into engagement with the mandrel 73 in a manner corresponding to that described with reference to FIGURE 19. At this point, the assembly and the valve secured thereto may be removed from the well string 120 by reversing flow therein, as described with reference to FIGURE 20. As with the removal of the insertion apparatus, the inclined upper surfaces of the side pockets and lower inclined surfaces of the springs 124 facilitate upward movement of the assembly within the well string 120.

To summarize, the apparatuses and method of the present invention provide means whereby tools may be inserted into and removed from preselected side pockets in well strings. The apparatuses are adapted to pass through curved flow lines to well strings disposed at inaccessible and remote locations. Although the method and apparatuses have been described with reference to the insertion of gas lift valves, it is to be understood that the invention may equally well be used for inserting and retrieving other tools from well strings. Furthermore, although the retrieving assemblies have been shown incorporating the retriever of FIGURE 11, the retriever shown in FIGURES 12 and 13 is adaptable for use with the assemblies of any of the embodiments of the invention.

The foregoing description of the invention is, therefore, merely intended to be explanatory thereof. Various changes in the details of the described method and illustrative constructions may be made, within the scope of the appended claims, without departing from the spirit of the invention.

I claim as my invention:

1. An apparatus for installing well tools in pockets disposed laterally of and in communication with the interior of a well string, said apparatus comprising:

a well string having laterally disposed pockets therein;

a carrier adapted to be pumped through the well string,

said carrier including packer means in fluid-tight engagement with the interior of the well string;

a tool connector carried by said carrier, said connector being adapted to release a tool connected thereto upon engagement of said tool with a laterally-disposed pocket of the well string;

means operatively associated with said connector to bias a tool received thereby towards the pockets disposed laterally of the well string; and

indexing means to facilitate positioning of a tool connected to said connector in a preselected pocket disposed laterally of the well string, said indexing means comprising first and second engageable portions included in the structure of said well string and said carrier, respectively.

2. An apparatus for installing well tools in pockets disposed laterally of and in communication with the interior of a well string extending into a formation disposed beneath a relatively deep body of water, said apparatus comprising:

a well string having laterally disposed pockets therein;

a carrier adapted to be inserted into the well string and propelled therethrough to the approximate location of the laterally disposed pockets by fluid pressure, said carrier including packer means in fluid-tight engagement with the interior of the well string;

a tool connector carried by said carrier and being adapted to release a tool connected thereto upon engagement of said tool with a pocket disposed laterally of the well string;

throw-over means operatively associated with said connector to bias a tool connected thereto towards the pockets disposed laterally of the well string;

and, indexing means to facilitate positioning of a tool connected to said connector in a preselected pocket disposed laterally of the well string, said indexing means comprising first and second engageable portions included in the structure of said well string and said carrier, respectively.

3. An apparatus according to claim 2 wherein said first and second portion of said indexing means comprise:

a selector groove disposed in said preselected pocket and communicating with the interior of said well string;

and, a selector element secured to said carrier and dimensioned to slide within said selector groove upon biasing of a tool received by the connector towards said preselected pocket.

4. An apparatus according to claim 2 wherein said first and second portions of said indexing means comprise:

a recess in the well string disposed adjacent to the preselected pocket;

and, expansible dogs secured to said carrier member in normally retracted condition, said dogs being adapted to expand into seating engagement with the recess in the well string upon being positioned adjacent to said recess.

5. An apparatus according to claim 2 wherein said first and second portions of said indexing means comprise:

a specifically dimensioned opening extending between said preselected pocket and the interior of said well string;

and, a spacer element secured to said carrier and dimensioned opening upon biasing of the tool connected thereto towards said preselected pocket.

6. An apparatus for installing well tools in pockets disposed laterally of and in communication with the interior of a well string extending into a formation disposed beneath a relatively deep body of water, comprising:

a well string having laterally disposed pockets therein;

a wellhead submerged within the body of water at the top of said well string, said Well string being operatively connected to said wellhead;

, a smoothly curved first flow line extending outwardly from said wellhead and communicating with said well string through said wellhead;

a second flow line extending into said Wellhead to provide for fluid circulation through said well string and said first flow line;

a carrier member adapted to be inserted into said first flow line and pumped therethrough into said well string, said carrier including packer means in fluidtight engagement with the interior of the Well string;

a tool connector carried by said carrier member and being adapted to release a tool connected thereto upon engagement of said tool in a pocket disposed laterally of the well string;

means operatively associated with said connector to bias a tool connected thereto towards the pockets disposed laterally of the well string;

and, indexing means to facilitate positioning'of a tool connected to said connector in a preselected pocket disposed laterally of the well string, said indexing means comprising first and second engageable portions included in the structure of said well string and said carrier, respectively.

7. An apparatus according to claim 6 wherein said first and second portions of said indexing means comprise:

a selector groove disposed in said preselected pocket and communicating with the interior of said well string;

and, a selector element secured to said carrier and dimeusioned to slide within said selector groove upon biasing of a tool received by the connector towards said preselected pocket.

8. An apparatus according to claim 6 wherein said first and second portions of said indexing means comprise:

a recess in the well string disposed adjacent to the preselected pocket;

and, expansible dogs secured to said carrier member in normally retracted condition, said dogs being adapted to expand into seating engagement with the recess in the well string upon being positioned adjacent to said recess.

9. An apparatus according to claim 6 wherein said first and second portions of said indexing means comprise:

a specifically dimensioned opening extending between said preselected pocket and the interior of said well string;

and, a spacer element secured to said carrier and dimensioned to direct said connector through said specifically dimensioned opening upon biasing of the tool connected thereto towards said preselected pocket.

10. An apparatus for removing well tools from pockets disposed laterally of and in communication with the interior of a Well string, said apparatus comprising:

a Well string having laterally disposed pockets therein;

a carrier adapted to be pumped through the well string,

said carrier including packer means in fluid-tight engagement with the interior of the well string;

a tool retriever carried by said carrier, said retriever being adapted to attach itself to a tool positioned in a laterally-disposed pocket of the well string;

means operatively associated with said retriever to bias the retriever towards the pockets disposed laterally of the well string in which a tool may be positioned;

and, indexing means to facilitate positioning of the retriever adjacent the preselected pocket which holds the tool to be removed, said indexing means comprising first and second engageable portions included in the structure of said well string and said carrier, respectively.

References Cited by the Examiner UNITED STATES PATENTS CHARLES E. OCONNELL, Primary Examiner.

JACOB L. NACKENOFF, Examiner,

C. H. GOLD, J. A. LEPPINK, Assistant Examiners. 

10. AN APPARATUS FOR REMOVING WELL TOOLS FROM POCKETS DISPOSED LATERALLY OF AND IN COMMUNICATION WITH THE INTERIOR OF A WELL STRING, SAID APPARATUS COMPRISING: A WELL STRING HAVING LATERALLY DISPOSED POCKETS THEREIN; A CARRIER ADAPTED TO BE PUMPED THROUGH THE WELL STRING, SAID CARRIER INCLUDING PACKER MEANS IN FLUID-TIGHT ENGAGEMENT WITH THE INTERIOR OF THE WELL STRING; A TOOL RETRIEVER CARRIED BY SAID CARRIERE, SAID RETRIEVER BEING ADAPTED TO ATTACH ITSELF TO A TOOL POSITIONED IN A LATERALLY-DISPOSED POCKET OF THE WELL STRING; MEANS OPERATIVELY ASSOCIATED WITH SAID RETRIEVER TO BIAS THE RETRIEVER TOWARDS THE POCKETS DISPOSED LATERALLY OF THE WELL STRING IN WHICH A TOOL MAY BE POSITIONED; AND, INDEXING MEANS TO FACILITATE POSITIONING OF THE RETRIEVER ADJACENT THE PRESELECTED POCKET WHICH HOLDS THE TOOL TO BE REMOVED, SAID INDEXING MEANS COMPRISING FIRST AND SECOND ENGAGEABLE PORTIONS INCLUDED IN THE STRUCTURE OF SAID WELL STRING AND SAID CARRIER, RESPECTIVELY. 